350 



MANUAL OF ZOOLOGY. 



" neurapophyses" because they form with the body a canal — ' 

 the " neural canal " — which encloses the spinal cord. Erom 

 the point where the neural arches meet behind, there is usually 

 developed a longer or shorter spine, which is termed the " spi- 

 nous process " or " neural spine " (s). From the neural arches 

 there are also developed in the typical vertebra two processes 

 (a a), which are known as the "articular" processes, or.".zyga- 

 pophyses." The vertebrse are united to one another partly by 

 these, but to a greater extent by the bodies or " centra." From 

 the sides of the vertebral body, at the point of junction with 

 the neural arches, there proceed two lateral processes (d d), 

 which are known as the " transverse processes." (In the typical 



Fig. 125. — A, Lumbar vertebra of a Whale : c Body or centrum ; « « Neural arches ; 

 J Neural spine : « a Articular processes ; ^rf Transverse processes. B, Diagram of a 

 thoracic vertebra : c Centrum ; « n Neural arches enclosing the neural canal i s 

 Neural spine ; r #■ Ribs, assisting in the formation of the hsemal arch ; pp Costal car- 

 tilages ; b Sternum, with haemal splrie. (After Owen.) 



vertebra the transverse processes consist each of two pieces, an 

 anterior piece or " parapophysis," and a posterior piece or 

 " diapophysis." These elements form the vertebra of the 

 human anatomist, but the " vertebra " of the transcendental 

 anatomist is completed by a second arch which is placed be- 

 neath the body of the vertebra, and which is called the " hae- 

 rnal" arch, as it includes and protects the main organs of the 

 circulation. This second arch is often only recognisable with 

 great difficulty, as its parts are generally much modified, but a 

 good exainple may be obtained in. the human cliest, or in the 

 caudal vertebra of a bony fish. 



The haemal arch in the case of the human thorax (fig. 125, 

 B) is formed by the ribs {r r) and the costal cartilages (//),. 



